Covalent complexes

Tris(2,2 -bipyridine)ruthenium(II) complex (Ru(bpy)3+) has been most commonly employed as a chromophore in the studies of photoinduced ET. Electrostatic effects on the quenching of the emission from the Ru(II) complex covalently bound to polyeletrolytes have been studied by several groups [79-82]. 

Recently, Suzuki-type reactions in air and water have also been studied, first by Li and co-workers.117 They found that the Suzuki reaction proceeded smoothly in water under an atmosphere of air with either Pd(OAc)2 or Pd/C as catalyst (Eq. 6.36). Interestingly, the presence of phosphine ligands prevented the reaction. Subsequently, Suzuki-type reactions in air and water have been investigated under a variety of systems. These include the use of oxime-derived palladacycles118 and tuned catalysts (TunaCat).119 A preformed oxime-carbapalladacycle complex covalently anchored onto mercaptopropyl-modified silica is highly active (>99%) for the Suzuki reaction of p-chloroacetophenone and phenylboronic acid in water no leaching occurs and the same catalyst sample can be reused eight times without decreased activity.120... 

Aida and Jiang recently reported an iron(II) porphyrin 1-methylimidazole complex covalently encapsulated within a large aryl ethereal dendrimer cage, as... 

Physical Intercalation Complexes, Covalent Binding and Hydrolysis... 

Fig. 16.8 Schematic of a diphosphine rhodium complex covalently tethered to a cross-linked styrene/divinylbenzene matrix, used for the hydrogenation of quinoline.

P. R. Ashton, R. Ballardini, V. Balzani, E. C. Constable, A. Credi, O. Kocian, S. J. Langford, J. A. Preece, L. Prodi, E. R. Schofield, N. Spencer, J. E Stoddart, S. Wenger, Ru(II)-Polypyridine Complexes Covalently Linked to Electron Acceptors as Wires for Light-Driven Pseudorotaxane-Type Molecular Machines , Chem. Eur. J. 1998, 4, 2411-2422. 

A similar study was performed on ruthenium-modified myoglobins, in which AG variations were obtained by changing the nature of the ruthenium complex covalently bound to the protein, and by substituting a porphyrin to the heme [137]. It is gratifying to observe that, in spite of the rather heterogeneous character of this series, the study leads to an estimation of 1.9 to 2.4 eV for A which is consistent with the value 2.3 eV derived in section 3.2.1 from temperature dependent experiments. Satisfactory agreement between the results given by the two methods is also observed in the case of ruthenium-modified cytochrome c [138]. 

The structure of the compound consists of two residues, one cationic (PYS-PYSH)+, containing the S-S bond linking the two 2-mercapto-pyridine molecules one of which is protonated and Ij as a counter anion. In the crystal lattice there are four symmetry-independent cation-anion pairs. There are only a few crystal structures reported in the literature containing open chain stable cations of DS-SD dimers, such as the monocationic [(C HgN S-SNjC Hj) ) ) [15]. The two I-I bond distances of the Ij" in the four components of complex (26) are 2.887(4) and 2.944(3) A in component a, 2.874(4) and 2.957(3) A in b, 2.968(3) and 2.862(3) A in c and 2.855(4) and 2.927(3) A in d, respectively, indicating a slight asymmetry of I3 in this complex (covalent hnear asymmetric). 

R)-BINAP/l,2-diphenylethylenediamine ruthenium(II) complexes covalently attached to polystyrene (Scheme 4.32) promote the asymmetric hydrogenation of aromatic ketones and of a, yS-unsaturated ketones [125]. The catalysts (52) and (53) were reused at high substrate/catalyst molar ratio (S/C) of 2470 in 14 experiments. Remarkably, the enantiopurity of the products remained high after each run, constantly being in the range of 97 to 98% ee. 

Baleizao, C. Gigante, B. Sabater, M. J. Garcia, H. Corma, A. (2002) On the activity of chiral chromium salen complexes covalently bound to solid silicates for the enantioselective epoxide ring o emag Applied Catalysis A General 228 279-288. 

Coordination bonds, between transition metal atoms and ligating atoms, 27 72-76 Coordination chemistry, of oligopyridines, see Oligopyridines, coordination chemistry Coordination complexes covalent binding in, 5 13-15 fluorocyclic derivatives, 15 346-368 Coordination compounds... 

Recent work by Nagata et al. ]75] has demonstrated the photoactivation of a cobalt porphyrin complex. Covalently... 

In aspect of chip-based technology, electrochemical genosensors based on different materials and transducers have been recently developed in response to clinical demand of giving promising results [18-25]. Different sensor technologies provide a unique platform in order to immobilize molecular receptors by adsorption, crosslinking or entrapment, complexation, covalent attachment, and other related methods on nanomaterials [5,7,26]. 

Fig. 7 Os(II) bipyridyl carbonyl complex covalently linked to both free base and Zn(II) tetraphenylporphyrin [45]...

A recent addition to this field is the polymer-supported di(2-pyridyl)-methylamine-palladium dichloride complex covalently attached to a styrene-alt-maleic acid anhydride copolymer. Turnover numbers as high as 105 were reported and a couple of microwave-heated Suzuki-Miyaura reactions could be performed in neat water [134], 2-Pyridinealdoxime-based Pd(II)-... 

To understand the subtlety and electronic structure of the complex covalent network of /9-R105 boron, it is useful to view the contents of the unit cell [Fig. 13.4.11(b)] as assembled from Bi2fl (at the center of a B84 cluster) and B57 (lying on a C3 axis) fragments connected by 2c-2e bonds. 

The occurrence of vectorial energy transfer (126, 195, 210-212) was reported for a zinc porphyrin species modihed with four trw-(4,4 -dimethyl-2,2 -bpy) ruthenium(ll) complexes covalently bound at the meso-positions (211), [ZnTBpyP Ru(dmbpy)2 4] (Fig. 23). 

Figure 22 Introducing normative prosthetic group into metalloproteins. (a) by chemical modification of heme propionate. (Reprinted with permission fi-om Ref. 25. 2002 the American Chemical Society) (b) by noncovalent addition strategy. The crystal stmcture of the Fe (3,3-Me2-salophen) incorporated into AlalTGlaMb. (Reprinted with permission from Ref 287. 2004 the American Chemical Society) (c) by a single attachment strategy. The computer model of adipoc)4e lipid binding protein-phenanthroline complex. (Reprinted with permission from Ref. 291. 1997 the American Chemical Society) (d) by a dual covalent attachment strategy. The computer model of Mb(L72C/Y 103C) with a Mn "-Salen complex covalently attached at two-points and overlayed with heme. (Reprinted with permission from Ref 288. 2004 the American Chemical Society)...

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